Mechanical tissues such as stone cells and endodermal cells are crucial components in many medicinal plants. Stone cells, like bast fibres, are branched or non-branched. Each group is then separated into subgroups according to wall structure (whether striated, pitted and striated, etc.), thickness of wall and cell cavity, color of walls and contents, absence of color and contents, etc. <Callout type="tip" title="Tip">Identifying these cells can help in authenticating herbal medicines.</Callout> Branched stone cells occur in witch-hazel bark (Plate 31, Fig. 2) and tea-leaf (Plate 31, Fig. i). Non-branched stone cells are divided into two main groups: porous and striated, and porous and non-striated. <Callout type="important" title="Important">The diagnostic stone cell of aconite is rectangular or square in outline with yellowish walls and a central cavity many times the thickness of the wall.</Callout> Endodermal cells vary greatly in form, color, structure, and composition of the wall. They can be divided into two groups: thin-walled parenchyma-like cells and thick-walled fibre-like cells. <Callout type="warning" title="Warning">The endodermal cells of aletris are yellowish brown, slightly porous and striated, making them distinct from other cells.</Callout> The hypodermal cells occur in sarsaparilla root and triticum, with their structure varying between rounded and elongated. <Callout type="gear" title="Gear">Microscopic examination tools are essential for identifying these cells accurately.</Callout>
STONE CELLS Stone cells, like bast fibres, are branched or non-branched. E^ch group is then separated into subgroups according to wall structure (whether striated, or pitted and striated, etc.), thick- ness of wall and of cell cavity, color of waU and of cell contents, absence of color and of cell contents, etc.
BRANCHED STONE CELLS Branched stone cells occur in a number of drugs. In witch- hazel bark (Plate 31, Fig. 2) the walls are thick, white, and very p)orous. In some cells the branches are of equal length; in others they are unequal. In the tea-leaf (Plate 31, Fig. i) the walls are yellowish white and finely porous. When the lower wall is brought in focus, it shows numerous circular pits. These pits represent the pores viewed from the end. The branches frequently branch or fork. Branched stone cells also occur in coto bark, acer spicatum, staranise, witch-hazel leaf, hemlock, and wild-cherry barks.
Non-branched stone cells are divided into two main groups, as follows: 1. Porous and striated stone cells, and, 2. Porous and non-striated stone cells. POROUS AND STRIATED STONE CELLS Porous and striated walled stone cells occur in ruellia root, winter's bark, bitter root, allspice, and aconite. These stone cells are shown in Plate 33, Figs, i, 2, 3, 4, and 5. The stone cells of ruellia root (Plate 32, Fig. i) are greatly elongated, rectangular in form, with thick, white, strongly porous walls. The central cavity is narrow and is marked with prominent pores and striations. The stone cells of winter's bark (Plate 32, Fig. 2) vary from elongated to nearly isodiametric. The pores are very large, Branched Stone Cells I. Tea leaf {Thrn sinensis. L.). 3. Witch-hazel bark {HamamcUi cirginiaHO, L.). 3. Hemlock bark {Tsuga canadrniis, [L.) Carr). 4. VVild-chcirj' bark (Pruuus seroUna, Ehrh.). MECHANICAL TISSUES 111 the light yellowish wall is irregularly thickened, and the central cavity is very large. The pores are prominent. The stone cell of bitter root (Plate 32, Fig. 3) is nearly isodiametric. The walls are yellowish white and strongly por- ous and striated. The central cavity is about equal to the thick- ness of the walls. The stone cell of allspice (Plate 32, Fig. 4) is mostly roimded in form, and when the outer wall only is in focus it shows nmner- ous round and elongated pores. The central cavity is filled with masses of reddish-brown tannin. The striations are very prominent. The diagnostic stone cell of aconite (Plate 32, Fig. 5) is rectangular or square in outline; the walls are yellowish and the central cavity has a diameter many times the thickness of the wall. The side and surface view of the pores is prominent, and the striations are very fine.
POROUS AND NON-STRIATED STONE CELLS Porous and non-striated stone cells occur in Ceylon cinna- mon, in calumba root, in dogwood bark, in cubeb, and in echi- nacea root. The diagnostic stone cells of Ceylon cinnamon (Plate 33, Fig. i) are nearly square in outline; the walls are strongly porous and the large central cavity frequently contains starch. The stone cells of caliunba root (Plate 33, Fig. 2) vary in shape from rectangular to nearly square, and the walls are greenish yellow, unequally thickened, and strongly porous. The typical stone cells contain several prisms, usually four. The stone cells of dogwood bark (Plate 33, Fig. 3) have thick, white walls with simple and branched pores. The cen- tral cavity frequently branches and appears black when recently mounted, owing to the presence of air. The stone cells of cubeb (Plate 33, Fig. 4) are very small, mostly rounded in outline, with a great nimiber of very fine simple pores which extend from the outer wall to the central cavity. The wall is yellow and very thick. The stone cells of echinacea root (Plate 33, Fig. 5) are very irregular in form; the walls are yellowish and porous, and the central cavity is very large. A black intercellular substance is usually adhering to portions of the outer wall.
The color of the walls of the different stone cells is ver' variable. In Ceylon dnnamon and ruellia the walls are color- less; in zanthoxylium, light yellow; in rumex, deep yellow; in cascara sagrada, greenish yellow. The pores of stone cells, like the pores of bast fibres, are either simple or branched, and they may or may not extend through the entire wall. Many of the shorter pores extend for only a short distance from the cell cavity. The width of the cell cavity varies considerably in the stone cells of the different plants. In aconite (Plate 32, Fig. 5), in calumba (Plate 33, Fig. 2), and in Ceylon cinnamon (Plate 33, Fig. i), the cell cavity is several times greater than the thick- ness of the cell wall. In allspice (Plate 32, Fig. 4), in bitter root (Plate 32, Fig. 3), the diameter of the cell cavity and the thickness of the wall are about equal. In cubeb (Plate 33, Fig. 4), in ruellia (Plate 32, Fig. i), the wall is thicker than the diameter of the cell cavity. The cavity of many stone cells contains no characteristic cell contents. In other stone cells the cell contents are as characteristic as the stone cell. The stone cells of both Saigon and Ceylon cinnamon (Plate 33, Fig. i) contain starch; the stone cells of caliunba (Plate 33, Fig. 2) contain prisms of calcium oxalate; the stone cells of allspice and sweet-birch bark contain tannin.
In cross-sections, stone cells occur singly, as in Saigon cinna- mon (Plate 34, Fig. i), ruellia (Plate 34, Fig. 2); in groups, as in cascara sagrada (Plate 34, Fig. 3) ; and in continuous bands, as in Saigon cinnamon (Plate 34, Fig. 4). In powdered drugs, stone cells, like bast fibres, occur singly, as in ruellia, calumba, etc. ; or in groups, as in cascara sagrada, witch-hazel bark, etc. In most powders they occur both singly and in groups. The individual stone cells are mostly entire, as in ruellia, calumba, allspice, echinacea, etc. In cascara sagrada many of the stone cells are broken when the closely cemented groups are torn apart in the milling process. Many of the branched Porous and Striated Stone Cells 1. Ruellia root (RueUia cHiosa, Pursh.). 2. Winter'B-bark (Drimyi winteri, Forst.)- 3. Bitterroot [Apocynum androsamifolium, L.). 4. Allspice (Pimenta officinalis, Lind).). 5. Aconite (Actmilum naptUus, L.). Porous and Non-Striated Stone Cells {cinnamomum seyianicvm, Nees). 1. Ceyli 2. Calumba root (Jaleorhiza palmalc, [Lai 3. D(^>-ood root bark {Cornus fiorida, t..). 4. Cubeb {Piper cubtba, L., i.) 5. Echinacea (Ethinacea angaslifolia, D.C.)- I. SaigoD cinnamon. 3. RuelUa root {RueUia cUiosa, Purih.). 3. Cascaia msrada {Rhamnus punkiana, D.C.). 4. SaigOD dnnamon. 116 HISTOLOGY OF MEDICINAL PLANTS stone cells of witch-hazel bark and leaf, wild cherry, etc., also occur broken in the powder. The walls of all stone cells are composed of lignin. The form of stone cells varies greatly; in aconite the stone cells are quadrangular; in ruellia they are rectangular; in pimenta, circular or oval in outline; in most stone cells they are polygonal. The lignified walls of stone cells are stained red with a solution of phloroglucin and hydrochloric acid, and the walls are stained yellow by aniline chloride.
ENDODERMAL CELLS The endodermal cells of the different plants vary greatly in form, color, structure, and composition of the wall, yet these different endodermal cells may be divided into two groups: first, thin-walled parenchyma-like cells, and, secondly, thick- walled fibre-like cells. In the thin-walled endodermal cells the walls are composed of cellulose, and the cell terminations are blunt or rounded. When the drug is powdered the cells break up into small diagnostic fragments. In the thick-walled endo- dermal cells the walls are lignified and porous, and the ends of the cell are frequently pointed and resemble fibres. Sarsaparilla root, triticum, convallaria, and aletris have thick-walled endodermal cells.
STRUCTURE OF ENDODERMAL CELLS The endodermal cells of sarsaparilla root (Plate 35, Fig. i) are never more than one layer in thickness. The walls are porous and of a yellowish-brown color. Alternating with the thick-walled cell is a thin-walled cell, which is frequently re- ferred to as a passage cell. The endodermal cells of triticum (Plate 35, Fig. 2) are yellow- ish and the walls are porous and striated. There are one or two layers of cells. The cells forming the outer layer have very thin outer but thick inner walls, while the cells fonning the inner layer are more uniform in thickness. The endodermal cells of convallaria (Plate 35, Fig. 3) are yellowish white in color, and the walls are porous and striated. Cross-Sbctions of Endodekual Cells of I. SarsaparilU root (Smilax officinalis, Kunth) . a. Triticum (Agropyron repens, L.). 3. Convallaria (Convatiaria majalis, L.) 4. Aktria (Aletris farinoia, L.). 118 HISTOLOGY OF MEDICINAL PLANTS The outer wall of the layer of cells is thinner than the inner wall. The innermost layer of cell is more uniformly thickened. The endodermal cells of aletris (Plate 35, Fig. 4) are yellow- ish brown, slightly porous and striated. There are one or two layers of these ceUs, and two of the smaller cells usually occupy a space similar to that occupied by the radically elongated single cell. On longitudinal view the endodermal cells of sarsaparilla triticum, convallaria, and aletris appear as follows: Those of sarsaparilla (Plate 36, Fig. i) are greatly elongated, the ends of the cells are blimt or slightly pointed, and the walls appear porous and striated. Those of triticum (Plate 36, Fig. 2) are elongated, the walls are porous and striated, and the outer wall is much thinner than the inner wall. The end wall between two cells frequently appears common to the two cells. Those of convallaria (Plate 36, Fig. 3) are elongated, and the end wall is usually blimt. The outer wall is thinner than the inner wall. Those of aletris (Plate 36, Fig. 4) are fibre-like in appear- ance; the ends of the cells are pointed and the wall is strongly porous. The longitudinal view of these cells is shown in plate 36.
HYPODERMAL CELLS Hypodermal cells occur in sarsaparilla root and in triticum. In the cross-section of sarsaparilla root (Plate 37, Fig. i) the hypodermal cells are yellowish or yellowish brown. The outer wall is thicker than the inner wall, the cell cavity is mostly rounded, and contains air. The walls are porous and finely striated. On longitudinal view the hypodermal cells of sarsa- parilla (Plate 37, Fig. 2) are greatly elongated; the outer and side walls are thicker than the inner walls. The ends of the cells are blunt and distinct from each other. In cross-section the hypodermal cells of tritiami (Plate 37, Fig. 3) are nearly roimded in outline, and the walls are of nearly uniform thickness. In longitudinal view (Plate 37, Fig. 4) the same cells appear parenchyma-like, and the walls between any two cells appear common to the two cells.
Key Takeaways
- Identification of stone cells is crucial for authenticating herbal medicines.
- Endodermal cells can be divided into thin-walled and thick-walled types, each with distinct characteristics.
- The structure and composition of endodermal cells vary significantly among different plants.
Practical Tips
- Use microscopic examination tools to accurately identify stone cells in powdered herbs.
- Recognize the diagnostic features of aconite's stone cells for quick identification.
- Understand that endodermal cells can be broken during milling, affecting their appearance in powder form.
Warnings & Risks
- Be cautious when handling samples containing tannin or other potentially harmful compounds.
- Incorrect identification of plant parts could lead to misdiagnosis and ineffective treatment.
- The presence of air bubbles in hypodermal cells can affect the accuracy of cell identification.
Modern Application
While the techniques described in this chapter are rooted in historical practices, they still hold relevance for modern herbalists and pharmacologists. The ability to identify stone cells and endodermal cells accurately remains crucial for ensuring the authenticity and efficacy of herbal medicines. Modern tools have improved precision but the fundamental knowledge of these cell structures is invaluable.
Frequently Asked Questions
Q: What are the diagnostic features of aconite's stone cells?
The diagnostic stone cell of aconite (Plate 32, Fig. 5) is rectangular or square in outline; the walls are yellowish and the central cavity has a diameter many times the thickness of the wall. The side and surface view of the pores is prominent, and the striations are very fine.
Q: How do endodermal cells differ between sarsaparilla root and triticum?
In sarsaparilla root (Plate 35, Fig. i), the endodermal cells are yellowish-brown, porous, and striated, with alternating thick-walled and thin-walled cells. In triticum (Plate 35, Fig. 2), these cells are yellowish, porous, and striated, forming one or two layers where outer walls are thinner than inner walls.
Q: What is the significance of hypodermal cells in sarsaparilla root?
Hypodermal cells in sarsaparilla root (Plate 37, Fig. i) are yellowish or yellowish brown with a thicker outer wall and mostly rounded cell cavities containing air. They appear elongated on longitudinal view.